1. Field of the Invention
The present invention relates to a process for removing tar from a spent acid. The present invention further relates to a process for removing by-product tar during the manufacture of isopropyl alcohol and methyl ethyl ketone.
2. Description of the Prior Art
Acids have been used in industrial hydrocarbon refining processes. For example, in indirect hydration processes for manufacturing isopropyl alcohol (IPA) and methyl ethyl ketone (MEK), concentrated sulfuric acid (e.g. 60% to 95% by weight) is employed as a catalyst for reactants. For economic reasons, sulfuric acid is captured and reused in the process. The sulfuric acid to be reused is in a dilute form referred to in the industry as xe2x80x9cspent acid.xe2x80x9d The spent acid is refined or concentrated by boiling off water, typically in a heater or heat exchanger.
A common problem encountered during the concentration of spent acid is the fouling of heater or heat exchanger surfaces. Fouling comes from the presence of dispersed tar, a reaction by-product, in the spent acid. Fouling necessitates more frequent cleaning and maintenance of the heat exchanger and reduces heat exchange efficiency.
U.S. Pat. No. 4,406,760 relates to the use of electrolytic process for treating sulfuric acid streams. Impurities are electrolytically oxidized. A disadvantage of the electrolytic process is the formation of hydrogen bubbles, which causes industrial hygiene and safety concerns.
Ind. Eng. Chem., Process Des. Dev., vol. 16, No. 4, 1977, discloses the use of air sparging, with cationic/nonionic surfactants to separate, low viscosity oil dispersions from water and sea water.
U.S. Pat. Nos. 5,080,802 and 5,156,747 disclose the use of a gas-producing eductor and coalescer to separate oil and particulate materials from liquids:
It would be desirable to have a process for removing tars from spent acid. It would further be desirable to have a process for removing tars from spent acid in indirect hydration processes for manufacturing IPA and MEK.
It is an object of the present invention to have a process for removing tar from spent acid.
It is an object of the present invention to have a, process for removing by-product tar from spent acid, in the manufacture of IPA and MEK.
According to this and other objects of the, present invention, there is a process for removing by-product tar during the manufacture of isopropyl alcohol. The process comprises the following a) reacting propyl with concentrated sulfuric acid and water to form isopropyl alcohol and a spent acid having a by-product tar therein; b) capturing at least a portion of the isopropyl alcohol c) contacting the spent acid with a gas in bubble form; d) allowing at least a portion of the tar to separate from the remainder of the spent acid to form a layer of tar and a layer of cleaned acid solution; e) capturing tar from the tar layer and disposing of it; f) capturing cleaned acid solution from the cleaned acid solution layer; and g) recycling the cleaned acid solution to step a) as a source of acid.
Still further according to this and other objects of the present invention, there is a process for removing by-product tar during the manufacture of methyl ethyl ketone. The process is substantially the same as the foregoing except that 1-butene is substituted for propylene.
Yet further according to this and other objects of the present invention, there is a process for removing tar from a spent acid. The process has the following steps: i) contacting the spent acid with a gas in bubble form for a time period sufficient to contact the tar; ii) allowing at least a portion of the tar to separate from the remainder of the spent acid to form a layer of tar; and iii) capturing the tar.